Present embodiments relate generally to measuring systems for determining rotor speed. More particularly, but not by way of limitation, present embodiments relate to methods of reducing error in rotor speed measurements.
Rotor speed may be utilized to make various determinations in operating characteristics of many types of rotating structures. For example, brake assemblies, engines, turbines, propeller shafts, fans, conveyors or any other rotating structure. The term “rotor” should be understood as a broadly defined rotating mechanical structure. Rotor speed is typically indicated in revolutions per minute (RPM), radians per second or hertz.
Generally, two methods of determining rotor speed or RPM are utilized. A frequency measurement system is utilized for fast rotating devices such as motors and turbines that typically rotate in thousands of revolutions per minute. Alternatively, period measurement system is more commonly utilized for structures having shafts that rotate at lesser speeds.
Sensors are normally utilized to determine rotor speed and may be embodied by shaft encoders, rotary pulse generators, proximity sensors or photoelectric sensors. In conjunction with the sensor, a rotor may include a target with one or more features which are measured during rotation of the rotor. These targets may have unintended geometric imperfections or intentional geometric inconsistencies which correspond to a location or condition of the rotor, such as top dead center of the rotor. For example, some targets may have a rib, tooth or other projection which is sized, shaped or spaced differently than other features of the target. Accordingly, these geometric imperfections introduce error into the measuring process which may result in propagation of such error through subsequent calculations based on the measuring process.
Accordingly, it would be desirable to develop methods in order to provide a more accurate system of measuring in order to reduce errors associated with known methods of measuring rotor speed.
The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded subject matter by which the scope of the instant embodiments are to be bound.